Seems that the stock piston is pretty durable; at least the way we use it. The new piston spec is 77.97 mm - 77.98 mm with a service limit of 77.89 mm. Our piston after 99.5 hours measured out at 77.95 mm. And 80+ of those hours were with the CCC mods and 13,000+ rpm rev limit. Unfortunately, I forgot to measure the ring gap of the old rings . We replaced the old piston with a 13.5:1 JE . The old piston looks pretty good, but that JE is mighty nice : Exhaust Side Intake Side "Left" Side "Right" Side Top As background, the bike began to use oil (and put it in the catch tube) at 10 hours when I did the CCC mods and jetted way too rich (I had a 170 MJ and needed a 148). I never saw puffs of smoke from the exhaust (and I always look on startup), so the oil useage must have been slow and continual. After I rejetted properly, the oil use stopped for quite a while, then came back. At rebuild time, the engine was using around 1/8" - 1/4" on the stick every 3 - 6 hours, but it wasn't consistent. The oil doesn't seem to have been coming through the intake guides as the back side of the intake valves are clean. When I pulled the piston, the ring gaps weren't aligned. There's no evidence of blow-by between the top and oil rings, but there is a lot of crud on the top of the piston. I suspect the oil use was around the rings, but without the old ring gaps, I can't be sure. I used a lot of HP4M with this piston so I could be seeing the combustion chamber contamination and oil useage that kelstr mentioned. Based on these observations, I'm going to keep the jetting right, and use only Rotella T for the new JE piston we put in.